Tag Archives: genetics

Brilliant Colors and Barbara McClintock

Since it’s the functional end of Fall, I figured I should at least give a quick nod that I’ve been meaning to do all season.

 

Around here you see dried maize a lot-often sold in bundles for Autumn decorations. I love the colors and the textures. They always make me think of apples (and the grudge that I didn’t get a single proper caramel apple this year) and gourds and Barbara McClintock.

 

(Shown here in a mixed media portrait by the fantastic chid0ri-take a spin through the galleries over there.)

 

She won a Nobel Prize in 1983 for her discovery of transposable genetic elements. The acknowledgement was a long time coming, it was for work that she’d essentially wrapped up by the early 1950s.

 

Barbara McClintock got her PhD from Cornell in 1927. In the 40s she began to concentrate on studying the inheritance of color in maize. In 1948 she discovered that two specific gene locations could physically swap locations.

 

She developed a theory that these mobile pieces regulated genes by either keeping them silent or allowing them to express themselves. It was these transposable elements-transposons (or jumping genes) that caused the fun colors and striping in maize.

 

Transposons are sequences of DNA that can move to new places within the genome of a cell. So calling them jumping genes, while fun to stay and more likely to stay in your mind, is not strictly accurate. They aren’t properly genes but instead known as mobile genetic elements.

 

Most scientists of her time were skeptical of her work. They credited her excellent microscope work but either argued that she’d misinterpreted something or else that such movement was yet another quirk of the corn species. (Whose genetics were already known to be complicated and irregular.)

 

She kept researching but stopped publishing her work by the 1950s, since it seemed that no one was inclined to pay attention to her discoveries. Her work was finally recognized decades later.

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Sunburn – Factoids and Public Service Announcement…

Even when it’s lovely and cool you can still sunburn, so cover up or put on some sunscreen!

 

I went to a fly-in on Sunday, it was so windy I had to hold my hat most of the day. Other than the flying hat, it was gorgeous weather. Enjoyed watching the planes take off and land. Didn’t get fantastic photos, but I felt like I was on the hunt trying to catch them and get my timing right.

I also learned firsthand just how much debris a helicopter sends flying…

 

Noticed a few hours after getting home that I was *really* pink. Oops!

 

After hunting down my aloe and downing a lot of water, I remembered reading something about the specific cause of sunburn.

 

Sunburn is the body’s reaction to damage to the skin cells caused by UV-B light.

 

Ultraviolet light damages cells by messing with their DNA.

 

If there are two thymine (the T of the famous CGAT) bases in a row it can cause them to fuse together. This puts a kink in the DNA strand. That messes with reading and replication and is what either kills or irritates the cells.

 

(There’s a more complex discussion here if you’re so inclined. I first ran across this factoid in Sam Kean‘s new book, The Violinist’s Thumb. Scientists have found that whether or not damage occurs depends on just where two Ts are stacked together when the ultraviolet light strikes. It takes tiny segments of a second for the damage to occur, which is part of the reason you can sunburn so quickly.)

 

Almost all animals and plants have enzymes to fix T-T kinks in DNA, but along some evolutionary path mammals lost them. Which is why we all can sunburn. Yay?

There was also a bit of a car show, everything was scrunched together, but I loved the idea of the massively overhauled hot rod reflected in the staid still original paint of a classic car.

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Heroes of Science II

I felt a little silly submitting a second piece to such a slimly attended contest, but I really wanted to do something with Rosalind Franklin’s work. I feel like she still generally gets less than due credit for her contributions to the basis of the study of genetics.

It’s also an eye of the beholder matter regarding the materials I chose.

I’ve seen these stones (if anyone remembers their name please let me know!) sold at many mineral shows, often as little miracles: “look at the naturally formed crosses.” It’s a great example of people seeing what they want to see. While the shape isn’t exact, to me it looks a lot more like that little round view with an “X” from Rosalind’s X-ray crystallography than it does a Christian cross.

(Of course, it could also be an X marks the spot, treasure here! Yar pirates!)

Rosalind Franklinwas a British scientist whose work on X-ray diffraction helped uncover the molecular structures of DNA, RNA, and assorted viruses amongst other substances. Her most famous ‘piece’ as it were, was the famous photo 51.

Photograph 51

This particularly clear X-ray crystallography image of DNA gave Watson and Crick the last piece of information to realize the true form of DNA. She was able to show that DNA had a corkscrew pattern in the shape of a helix- the question at the time was whether it has two or three chains.

Watson and Crick used her photo (the jury is still out on whether or not they got their hands on her work legitimately or not-Watson at least has become well known for his patronizing dismissal of her as a proper scientist) to determine the overall shape and played with the shapes of the molecular bases, realizing that sets of two would fit together with hydrogen bonding while others would repel each other on the same principle.

The double helix model with attracting/repelling bases also illustrated how simple (in theory!) replication is: essentially the strands split apart and naturally attract the right bases, so you end up with two copies of the original.

So a Mendel tribute for contributions to the models of inheritance and Franklin tribute for contributions to the material of inheritance.

I’ve mentioned the series before, but for a quick and dirty introduction to genetics, take a look at Larry Gonick and Mark Wheelis’s Cartoon Guide to Genetics. It’s a fast and fantastic introduction to the subject that gives a nice overview of the subject and it’s historical basis.

The classic text is going to be John Watson’s The Double Helix, which is brilliant of course, though I do find him teeth gratingly egotistical and sexist at times. Take a look at Brenda Maddox’s Rosalind Franklin: Dark Lady of DNA for a good, seemingly pretty balanced view of Franklin’s contrubutions.

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Heroes of Science I

A group on the deviantart website, Domain of Darwin, had a “Celebrating the Heroes of Science” contest.

It was sadly poorly attended. I wonder if it was in part because the subject seemed so intimidating, but so interesting. Especially for artisan crafters. I love science, especially biology, but it generally doesn’t inform my crafts nearly as much as history or literature does. So for me it was a nice ‘reach’ experiment, though my final pieces fell short of what I wanted, it gave me something to build on.

The two ‘heroes of science’ whose work I decided to portray were Gregor Mendel, whose practical experiments with plants laid the groundwork for the rules of inheritance, and Rosalind Franklin, whose X-ray crystallography helped provide the breakthrough in the search for the molecular structure of DNA.

Gregor Mendel did experimentation into inheritance decades before science was aware of the existence of genes, let alone of DNA. His most famous experiments were with pea plants, so their variations are what I chose to represent in my piece.

By crossing true breeding pea plants, each with their own set of true breeding physical attributes, he was able to observe that nature of inheritance generation after generation. His first surprise was that traits didn’t blend. A tall plant crossed with a short plant did not result in a middle height plant. Instead it resulted in tall plants. In breeding that second generation there came another surprise. The short trait didn’t disappear. He discovered that a certain percentage of the progeny of this second generation were short, and that those short plants were true breeding. A much larger percentage of the generation were tall, some of them breeding true, while others continued to split according to the same division as their parents. With a great deal of patience, cross breeding, time and math, Mendel discerned that certain traits-for instance ‘tallness’ were dominant and could ‘overrule’ but not remove the trait of ‘shortness’ in peas. Traits could be shuffled but were immutable. (Mostly…) 

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